Research On Path Loss Prediction Method And Application Of Radio Wave Propagation

Accurate loss prediction of radio wave propagation is the basis for reasonable planning, designand performance optimization of wireless network. With the rapid increase of mobile communicationusers and the demand of the faster communication rate, microcell and picocell system is widelyadopted. Typical radio wave propagation environment for micro cellular is in the urban canyon, whichleads to the invalidation of the conventional empirical prediction model based on measured data. Atthe same time, the rail transit planning and construction in our country has developed rapidly in recentyears, which greatly ease the contradiction between the development of urbanization and urban trafficfacilities. In order to realizing a complete wireless coverage in rail transit, it is particularly importantto study the wave propagation in the tunnel environment. Therefore, in this paper, we make a detailedstudy on the deterministic models such as ray-tracing model and Gaussian beam tracing model, andapply them to the urban and tunnel environment, which is not only of important theoreticalsignificance but also of broad application prospect.First of all, statistical model is studied and the shortcoming of the model is that it must bemodified according to similar scenes. The deterministic model like ray tracing is studied in detail, andwe propose a3D reverse ray tracing method based on visible walls and a new heuristic uniformdiffraction coefficient for nonperfectly conducting wedges. What’s more, numerical simulation isapplied in Ottawa city scene, of which the result shows that the prediction error is less than8dB.Secondly, as to the shortcomings of ray tracing like initial ray division, reception ball andcomplex diffraction, a new predicting model based on Gaussian beam tracing method is adopted. Theexpansion of source field, the propagation of Gaussian beams and the superposition of transformedbeam fields are specifically studied. Simulation result in complex metropolis environment exposes theshortcoming of traditional Gaussian beam-tracing method like time consuming. Some improvedmethod like space dividing and key region selection is proposed. Simulation in some different scenesis also made to verify the improved Gaussian beam tracing model is general in different scenes.Finally, as to the application demand of wireless network layout planning in subway tunnels, theradio wave propagation characteristics and spatial modeling in tunnel environment are researched.And we apply the3D reverse ray tracing method to the wave propagation prediction in differentsubway tunnels, which demonstrates both theoretical and applied values of the research in this paper.